This invention is in the area of processes and materials, and encompasses particles whose dispersion in aqueous media results in environmental benefits and which are removable from the environment by means of applied magnetic field. The particles possess a core/shell structure with a magnetic core and a functional shell.
Magnetic separation is a means by which complex separations may be accomplished. In this context, functional magnetic-particles in aqueous solution, termed magnetic fluids, have found particular use. The application of high gradient magnetic separation (HGMS), which uses a magnetic field to separate magnetic particles from suspension, has been exploited such that when these particles are attached to biological materials of interest (e.g., cells, drugs), the material of interest or target material may thereby be separated from other materials not bound to the magnetic-particles.
Functional magnetic nanoparticles that are separated using a magnetic field have been described in U.S. Pat. No. 7,795,041 to Hatton et al., the content of which is incorporated herein by reference in its entirety. However, thus described magnetic nanoparticles directly embedded into and non-covalently bound with a polymer matrix comprising one or multiple polymers are lacking in chemical stability, which leads to the loss of magnetization of the particles over time and particle dissolution under conditions of the environment.
U.S. Pat. No. 7,524,630 to Tan et al. the content of which is incorporated herein by reference in its entirety, describes nanoparticles having a core/shell structure with a magnetic core and a silicon oxide shell functionalized with biologically active molecules such as antibodies and nucleotides. The nanoparticles of U.S. Pat. No. 7,524,630 are disclosed to be useful to label cells, to detect and isolate nucleic acid molecules having specific nucleotide sequences, and to separate a mixture of different nucleic acid molecules. More specifically, U.S. Pat. No. 7,524,630 discloses a pre-formed silica surface being conjugated with at least one functional group comprising an oligonucleotide in the form of a molecular beacon, wherein the sequence of said oligonucleotide comprises a single-stranded loop structure comprising a nucleic acid sequence of interest. However, biologically active molecules such as nucleotides or antibodies conjugated to the particle surface are rapidly consumed and degraded by deleterious compounds present in the environment and thus cannot be used for aqueous remediation and as synthetic antiseptics.
U.S. Pat. No. 6,548,264 to Tan et al. discloses silica-coated nanoparticles and a process for producing silica-coated nanoparticles. Silica-coated nanoparticles in accordance with U.S. Pat. No. 6,548,264 are prepared by precipitating nano-sized cores from reagents dissolved in the aqueous compartment of a water-in-oil microemulsion. A reactive silicate is added to coat the cores with silica. The method employs a microemulsion, i.e., isotropic and thermodynamically stable single-phase system, to produce nanoparticles cores of a predetermined, very uniform size and shape. Cores produced using the microemulsion are then coated with silica using a silicating agent. The nanoparticles thus formed can be customized for a particular application by derivatizing various chemical groups onto the pre-formed silica coating. However, the microemulsion synthesis of the nanoparticles in accordance with U.S. Pat. No. 6,548,264 is cumbersome and cannot be readily scaled up and requires purification of the particles from the surfactant employed to create the microemulsion in the first place.